[WebAssembly] Correctly check end_if/end_try with else/catch

[aheejin]

Summary

When we encounter an else, catch, or catch_all, we currently just
push the structure NestingType and don't preserve the original if
and try's signature. So after we pass else/catch/catch_all, we
can't check if the values on stack have the correct types when we
encounter end_if or end_try. This CL fixes the issue, and modifies
the existing test to be correct (some of them had try without
catch).

[aheejin]

Small cosmetic fix

[aheejin]

Rebase

[aheejin]

Rename a function

llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp

case If:
       return {"if", "end_if"};
     case Else:
       return {"else", "end_if"};
     default:
       llvm_unreachable("unknown NestingType");
     }
   }
 
-  void push(NestingType NT) { NestingStack.push_back({NT, wasm::WasmSignature()}); }
+  void push(NestingType NT, wasm::WasmSignature Sig = wasm::WasmSignature()) {
+    NestingStack.push_back({NT, Sig});
+  }
 
   bool pop(StringRef Ins, NestingType NT1, NestingType NT2 = Undefined) {
     if (NestingStack.empty())
       return error(Twine("End of block construct with no start: ") + Ins);
     auto Top = NestingStack.back();
     if (Top.NT != NT1 && Top.NT != NT2)
       return error(Twine("Block construct type mismatch, expected: ") +
                    nestingString(Top.NT).second + ", instead got: " + Ins);
     TC.setLastSig(Top.Sig);
     NestingStack.pop_back();
     return false;
   }
 
+  // Pop a NestingType and push a new NestingType with the same signature. Used
+  // for if-else and try-catch(_all).
+  bool popAndPushWithSameSignature(StringRef Ins, NestingType PopNT,
+                                   NestingType PushNT) {
+    if (NestingStack.empty())
+      return error(Twine("End of block construct with no start: ") + Ins);
+    auto Sig = NestingStack.back().Sig;
+    if (pop(Ins, PopNT))
+      return true;
+    push(PushNT, Sig);
+    return false;
+  }
+
   bool ensureEmptyNestingStack(SMLoc Loc = SMLoc()) {
     auto Err = !NestingStack.empty();
     while (!NestingStack.empty()) {
       error(Twine("Unmatched block construct(s) at function end: ") +
                 nestingString(NestingStack.back().NT).first,
             Loc);
       NestingStack.pop_back();
     }
if (Name == "block") {
       ExpectBlockType = true;
     } else if (Name == "try") {
       push(Try);
       ExpectBlockType = true;
     } else if (Name == "if") {
       push(If);
       ExpectBlockType = true;
     } else if (Name == "else") {
-      if (pop(Name, If))
+      if (popAndPushWithSameSignature(Name, If, Else))
         return true;
-      push(Else);
     } else if (Name == "catch") {
-      if (pop(Name, Try))
+      if (popAndPushWithSameSignature(Name, Try, Try))
         return true;
-      push(Try);
     } else if (Name == "catch_all") {
-      if (pop(Name, Try))
+      if (popAndPushWithSameSignature(Name, Try, CatchAll))
         return true;
-      push(CatchAll);
     } else if (Name == "end_if") {
       if (pop(Name, If, Else))
         return true;
     } else if (Name == "end_try") {
       if (pop(Name, Try, CatchAll))
         return true;
     } else if (Name == "delegate") {
       if (pop(Name, Try))

llvm/test/MC/WebAssembly/type-checker-errors.s

# CHECK: :[[@LINE+1]]:3: error: end got i32, expected f32
   end_function
 
 end_if_insufficient_values_on_stack_2:
   .functype end_if_insufficient_values_on_stack_2 () -> ()
   i32.const 1
   if i32
   i32.const 2
   else
-# FIXME: Should complain about insufficient values on the stack.
+# CHECK: :[[@LINE+1]]:3: error: end: insufficient values on the type stack
   end_if
   drop
   end_function
 
 end_if_type_mismatch_2:
   .functype end_if_type_mismatch_2 () -> ()
   i32.const 1
   if i32
   i32.const 2
   else
-# FIXME: Should complain about a type mismatch.
   f32.const 3.0
+# CHECK: :[[@LINE+1]]:3: error: end got f32, expected i32
   end_if
   drop
   end_function
 
 else_insufficient_values_on_stack:
   .functype else_insufficient_values_on_stack () -> ()
   i32.const 1
   if i32

 # CHECK: :[[@LINE+1]]:3: error: popped f32, expected i32
   else
   i32.const 0
   end_if
   drop
   end_function
 
 .tagtype tag_i32 i32
+.tagtype tag_f32 f32
 
 end_try_insufficient_values_on_stack:
   .functype end_try_insufficient_values_on_stack () -> ()
   try i32
+  i32.const 0
+  catch_all
 # CHECK: :[[@LINE+1]]:3: error: end: insufficient values on the type stack
   end_try
+  drop
   end_function
 
 end_try_type_mismatch:
   .functype end_try_type_mismatch () -> ()
   try i32
-  f32.const 1.0
+  i32.const 0
+  catch tag_f32
 # CHECK: :[[@LINE+1]]:3: error: end got f32, expected i32
   end_try
+  drop
   end_function
 
 catch_insufficient_values_on_stack:
   .functype catch_insufficient_values_on_stack () -> ()
   try i32
 # CHECK: :[[@LINE+1]]:3: error: end: insufficient values on the type stack
   catch tag_i32
   end_try